1. Field of the Invention
This invention relates in general to polyurethanes, chain extenders, and processes for making and using them. The process relates in particular to certain dialkyl-m-phenylenediamines. The invention is also germane to reaction injection molding (RIM), reinforced reaction injection molding (RRIM), and cast elastomer processes for making polyurethanes including the products made thereby, especially automobile parts.
II. Description of the Prior Art
It is known to prepare useful polymers from the polyaddition reaction of isocyanates with polyols and diamines. Such polymers are made as elastomers, fibers, coatings, adhesives, as well as rigid and flexible foams.
Cast elastomers are made by carrying out the polymerization in a mold, usually at elevated temperature. Products from cast elastomer processes include tires, conveyor belts, and many other articles.
Since the development of reaction injection molding (RIM) processes in West Germany and elsewhere, polymer products have been made thereby for various purposes. These products include high density, integral skin rigid foams as well as automobile fascia (bumpers), grills, and the like. The products are formed in seconds from positively controlled mixing heads or by other static impingement mixing means. A further description of the RIM process may be found in U.S. Pat. No. 4,314,962 which is incorporated herein by reference.
Furthermore, a reinforced RIM (RRIM) process has been developed wherein the injection materials have contained therein prior to reaction, reinforcing fibers, metals, or other shapes/materials to strengthen the resultant products. RRIM products offer a variety of uses not previously available with RIM products since the physical or other properties may be changed by the reinforcing members.
In the past, diethyltoluene diamines and similar aromatic amines have been used, in a relatively pure form, as chain extenders in RIM, RRIM, and cast elastomer processes. Such processes are disclosed in U.S. Pat. No. 3,428,610 and 4,218,543. Those patents and others disclose such diamines as 2,5-diaminoxylene, 2,4-diaminomesitylene, 3,5,3',5'-tetra-ethyl-4,4'-diaminodiphenylmethane, 1-methyl-3,5-diethyl-2,4-diaminobenzene, and 1,3,5-triethyl-2,4-diaminobenzene. Such chain extenders, used in pure form reliably produce products of specified characteristics in a repeatable mold time. Of course, variation of the reactant polyhydroxy or polyisocyanate will also vary the characteristics and gel/hardening times. Notably, however, the mold times are most readily regulated by the use of predetermined chain extenders.
The only notable chain extender diamine which is formed as a mixture is the mixture of 1-methyl-3,5-diethyl-2,4-diaminobenzene and 1-methyl-3,5-diethyl-2,6-diaminobenzene, commonly referred to as diethyltoluene diamine (DETDA).
There exists a need for a greater variety of chain extenders to be used with conventional polyols and isocyanate-containing compounds. New chain extenders are needed to provide a spectrum of gelation and firm times as well as to create polyurethanes containing different structures which impart desirable mechanical, electrical, or other properties.
There also exists a need for very fast reacting chain extenders. Fast extenders can be used with rapidly operating RIM equipment which increases production rates for polyurethane molded products.
There also exists a need for reduction in the cost of RIM processing and a need to reduce or eliminate the use of external mold release agents.